Bell unit | Article about Bell unit by The Free Dictionary Bell unit | Article about Bell unit by The Free Dictionary decibel (dĕs`əbĕl', –bəl), abbr. dB, unit used to measure the loudness of sound sound, any disturbance that travels through an elastic medium such as air, ground, or water to be heard by the human ear. When a body vibrates, or moves back and forth (see vibration), the oscillation causes a periodic disturbance of the surrounding air or other medium that ..... Click the link for more information. . It is one tenth of a bel (named for A. G. Bell), but the larger unit is rarely used. The decibel is a measure of sound intensity as a function of power ratio, with the difference in decibels between two sounds being given by dB=10 log10(P1/P2), where P1 and P2 are the power levels of the two sounds. The faintest audible sound, corresponding to a sound pressure of about 0.0002 dyne per sq cm, is arbitrarily assigned a value of 0 dB. The loudest sounds that can be tolerated by the human ear are about 120 dB.

The level of normal conversation is about 50 to 60 dB. The decibel is also used to measure certain other quantities, such as power loss in telephone lines. Decibel A logarithmic unit used to express the magnitude of a change in level of power, voltage, current, or sound intensity. A decibel (dB) is 1/10 bel. In acoustics a step of 1 bel is too large for most uses. It is therefore the practice to express sound intensity in decibels. The level of a sound of intensity I in decibels relative to a reference intensity IR is given by notation (1). (1) Because sound intensity is proportional to the square of sound pressure P, the level in decibels is given by Eq. (2). (2) The reference pressure is usually taken as 0.0002 dyne/cm2 or 0.0002 microbar. (The pressure of the Earth's atmosphere at sea level is approximately 1 bar.) See Sound pressure The neper is similar to the decibel but is based upon natural (napierian) logarithms. One neper is equal to 8.686 dB.

Decibel a fractional unit of the bel (a unit of relative logarithmic value—the common logarithm of the ratio of two synonymous physical quantities, such as energy, power, or sound pressure). The decibel is equal to 0.1 bel. Symbols: Russian, db; international, dB. In practice the decibel is more often used than the bel, the basic unit. decibel [′des·ə‚bel] (physics) A unit for describing the ratio of two powers or intensities, or the ratio of a power to a reference power; in the measurement of sound intensity, the pressure of the reference sound is usually taken as 2 × 10-4 dyne per square centimeter; equal to one-tenth bel; if P1 and P2 are two amounts of power, the first is said to be n decibels greater, where n = 10 log10(P1/ P2). Abbreviated dB. decibel The unit in which the level , 4 of various acoustical quantities is expressed. decibel 1. a unit for comparing two currents, voltages, or power levels, equal to one tenth of a bel 2.

a similar unit for measuring the intensity of a sound. It is equal to ten times the logarithm to the base ten of the ratio of the intensity of the sound to be measured to the intensity of some reference sound, usually the lowest audible note of the same frequency deciBel A unit of measurement of the loudness or strength of a signal. One deciBel is considered the smallest difference in sound level that the human ear can discern. Created in the early days of telephony as a way to measure cable and equipment performance and named after Alexander Graham Bell, deciBels (dBs) are a relative measurement derived from two signal levels: a reference input level and an observed output level. A deciBel is the logarithm of the ratio of the two levels. One Bel is when the output signal is 10x that of the input, and one deciBel is 1/10th of a Bel. A whisper is about 20 dB. A normal conversation is typically from 60 to 70 dB, and a noisy factory from 90 to 100 dB. Loud thunder is approximately 110 dB, and 120 dB borders on the threshold of pain.

See dBm . INCREASE IN POWER LEVELS (WATTS)Formula is dB=10*log(P1/P2)DeciBels Output Signal Strength 3dB 2x 6dB 4x 10dB (1 Bel) 10x 20dB 100x 30dB 1,000x 40db 10,000x ATTENUATION OF AMPLITUDE (VOLTS or AMPS)Formula is dB=20*log(A1/A2)DeciBels Output Signal Strength -3dB 0.707x -6dB 0.5x -10dB 0.316x -20dB 0.1x -30dB 0.032x -40db 0.010x Bels and Bells Quite a lot was named after Alexander Graham Bell. Throughout the 20th century, the Bell name was ubiquitous. It will live on with the deciBel.

Bell unit - definition of Bell unit by The Free Dictionary Bell unit - definition of Bell unit by The Free Dictionary range of human hearing in decibels de·ci·bel (dĕs′ə-bəl, -bĕl′) n. Abbr. dB A unit used to express relative difference in power or intensity, usually between two acoustic or electric signals, equal to ten times the common logarithm of the ratio of the two levels. (ˈdɛsɪˌbɛl) n 1. (Units) a unit for comparing two currents, voltages, or power levels, equal to one tenth of a bel 2. (Units) a similar unit for measuring the intensity of a sound. It is equal to ten times the logarithm to the base ten of the ratio of the intensity of the sound to be measured to the intensity of some reference sound, usually the lowest audible note of the same frequency Abbreviation: dB (ˈdɛs əˌbɛl, -bəl) n. a unit used to express differences in power, esp. in acoustics or electronics: equal to ten times the common logarithm of the ratio of two signals.

Abbr.: dB de·ci·bel (dĕs′ə-bəl) A unit used to measure the loudness or intensity of a sound. The speaking voice of most people ranges from 45 to 75 decibels. See Note at sound 1. decibel 1. A logarithmic unit of sound intensity. 2. (dB) A measure of relative sound intensity. ThesaurusAntonymsRelated WordsSynonymsLegend: decibel Encyclopedia > Science and Technology > Physics > Physics decibel decibel (dĕsˈəbĕlˌ, –bəl) [ key ], abbr. dB, unit used to measure the loudness of sound . It is one tenth of a bel (named for A. G. Bell), but the larger unit is rarely used. The decibel is a measure of sound intensity as a function of power ratio, with the difference in decibels between two sounds being given by dB = 10 log10(P1/P2), where P1 and P2 are the power levels of the two sounds.

The faintest audible sound, corresponding to a sound pressure of about 0.0002 dyne per sq cm, is arbitrarily assigned a value of 0 dB. The loudest sounds that can be tolerated by the human ear are about 120 dB. The level of normal conversation is about 50 to 60 dB. The decibel is also used to measure certain other quantities, such as power loss in telephone lines. The Columbia Electronic Encyclopedia, 6th ed. Copyright © 2012, Columbia University Press. All rights reserved. See more Encyclopedia articles on: Physics Convert decibel [dB] <—> bel [B] • Acoustics — Sound • Sound Level • Compact Calculator 0.00001 Sound equipment. Rogers CityTV Studio. Toronto, Ontario, Canada. This table shows how the logarithmic scale can describe very big and very small numbers representing power, energy or amplitude ratios with much shorter notation. Human ears are very sensitive. You can hear everything from whisper at 10-meter distance to the noise of jet engines.

In terms of power, the sound of a firecracker can be 100,000,000,000,000 times more powerful than the faintest sound that the typical human ear can detect (20 micropascals). That’s a very big difference! Since the range of sound intensities that the human ear can detect is so huge, a logarithmic scale is used for measuring sound intensity. On the decibel scale, the faintest sound, also known as the threshold of hearing, is assigned a level of 0 decibels. A sound that is 10 times more intense is assigned a level of 20 decibels. A sound that is 100 times more intense is assigned a level of 30 decibels.

The list below shows some common sounds and their decibel level: Hearing threshold — 0 dB Whisper at 1 m distance — 20 dB Quiet conversation at 1 m distance — 50 dB Powerful vacuum cleaner at 1 m distance — 80 dB Hearing loss threshold if exposure is long — 85 dB Portable media player at maximum volume — 100 dB Threshold of pain — 130 dB Fighter aircraft jet engine at 30 m distance — 150 dB Stun grenade M84 at 1.5 m distance — 170 dB Music The sound level of a single violin at close distance is 82 to 92 dB. Los Angeles Children’s Orchestra performing at Central Park, New York, 2013. According to archeologists, music has been present in human life for as long as 50,000 years. It is found in every culture, and scientists believe that it is so widespread because it allows groups of people to bond. These bonds form between mothers and infants during the mother’s song, between people during traditional dancing and singing events, and during modern day concerts.

Most people like patterns, therefore music attracts us because it is structured and rhythmical. Noise Pollution Some of the noise is extremely unpleasant; it is often called noise pollution. This term refers to unwanted noise in the environment. It can be caused by a variety of sources and often results in discomfort, annoyance, and a range of unpleasant physiological and psychological responses, such as insomnia, fatigue, irregular blood pressure, damaged hearing when the noise pollution is severe, and other problems. Sources Noise pollution is often caused by the transportation, in particular airplanes, trains, and cars. In the industrial zone machinery also contributes to the pollution. Sometimes residents near wind turbines complain of the noise that the turbines produce. Construction can cause noise pollution as well. In some countries many households keep dogs outdoors, often for security reasons. When these dogs start barking because of people and animals passing by or because other dogs are barking, they contribute to the noise pollution. Finally, music from bars, restaurants, and individual homes can result in considerable loud noises.

WindShare’s Ex Place turbine in Toronto, Ontario generates approximately 1 million kWh per year of clean wind power Wind Turbines Some of the wind energy watch organizations report that low-frequency noise that wind turbines generate causes sleep disturbances, headaches, and other symptoms that are uncomfortable enough to force some people to move away from their homes, that are located near wind turbines. Wind power enthusiasts claim that the problem is in people’s perception of how the pollution affects them, not in the real negative effects that sound pollution has on people. Currently there are not enough reliable longitudinal investigations, therefore it is hard to evaluate the problems with the sound pollution caused by the turbines. It is important to continue research in this area to ensure that wind energy is used in a way that does not harm people who live nearby. Trains Squeaky railway car disk brakes Due to the noise pollution caused by trains, designers that build tracks as well as train parts manufacturers are constantly working on improving the design, to minimize this pollution. One of the main noise sources is the sound caused by the undulations that happen when the wheels roll on the rail. The sound is called the rolling noise. This problem is studied by using simulations of the rail track and the wheel.

By making the wheel and the rail vibrate less and with less intensity the noise can be reduced. Refining the construction of the breaks is one solution, and in recent years considerable improvements have been made to reduce noise by using new designs of some parts of the break mechanism. A noise barrier between the train tracks and a residential area The way the tracks are constructed can impact this noise as well. Some of the solutions for limiting noise pollution include building barriers around the tracks, similar to those used around highways. Some unavoidable noise pollution comes from the warning systems that the train operators use. For example, train crossings and trains are equipped with horns and other sound notification systems to make the pedestrians and drivers aware that the train is coming. This is to ensure sufficient awareness even if the visibility is limited or the pedestrians are visually impaired. The Fouga Magister jet trainer flying in a residential area in Toronto, Ontario, Canada Airplanes Aircraft noise is caused mainly from operating the jet and turboprop engines. It is a problem for the passengers and crew inside the aircraft and for the people who live near airports. The noise in the cabin, while the aircraft is in the air, is about 80 decibels.

To address this problem some passengers wear active noise-cancelling headphones, described below. Even in residential areas many countries do not regulate the minimum height for the aircrafts to fly or the maximum duration of time that they can stay above a given area. Generally the airspace, which is open for flight of aircrafts, can be used 24 hours a day. To address the noise pollution by aircraft governments often issue a list of recommendations on how to reduce the noise pollution for companies and organizations in the aviation industry. New York traffic Automobiles Automobiles have long been a source of noise pollution, especially in urban areas. At higher speeds the tires rolling against the road make the most noise. When drivers use winter tires in the summer or drive all-road vehicles on the highway, they increase the noise pollution because winter and all-road tires are designed to have higher friction so that they have better grip with the road even in icy or off-road conditions. The increased friction contributes to the noise. When the cars move slowly, the engine is a greater source of noise. To minimize the noise pollution manufacturers are working on creating quieter cars. At the same time cars are soundproofed, and new methods of active noise control are being designed to reduce the sounds inside of the car.

This can be achieved by creating an opposite-phase wave for the sound wave that causes the noise. Active noise control, discussed below in more detail, is also used in other systems, such as in noise cancellation for headphones. Highly efficient highway glass noise barrier in Nagoya, Japan Highways and large roads often have protective walls that keep the sound within the area. Some of these walls work so well, that the cars are barely audible to an average person, listening on the other side of the wall. This depends on the wall design, however. Some sound barriers are only good for blocking the sound on the ground level and do not protect people who live in high-rises. Electric cars are much quieter than the gasoline ones, due to their construction. It is a welcome improvement in the battle with noise pollution, but electric cars that are too quiet do not warn the pedestrians that the car is approaching; therefore some noise is generated artificially to ensure road safety. Construction at the Clarkson GO Train Station parking lot in Mississauga, Ontario, Canada Construction and Maintenance Construction work and maintenance, including the engineering work at the railway tracks and roads contributes to some noise pollution.

Some places have to do this work outside of the regular business hours, when the infrastructure systems under construction are not used as much by the public. Much of this noise is inevitable and difficult to regulate. In many countries one requires a permit to start construction, and may have to abide by rules such as not performing work at night or during the holidays. Household and Other Noise While it is difficult to regulate household noise through legislation, outside noise-producing activities are often restricted by by-laws. For example, in some areas all or some types of fireworks are banned outside of special national holiday celebrations. The sound level maximum limit can also be set for fireworks. Many government bodies that monitor the noise pollution provide guidelines for residents on how to reduce their noise output. Suggestions include notifying the neighbours of upcoming noise-related events, performing noise-generating activities during waking hours of the majority of people, training dogs not to make noise, and placing noise-generating appliances away from the walls that may carry the sound to the neighbours. In a number of countries it is acceptable to call the police if the noise from the neighbours’ activity is too disturbing. Some buildings, especially apartments, provide poor soundproofing, therefore it is important to check the space carefully before renting or purchasing it.

Here are some of things you can do: A noisy neighbourhood in New York Ask a friend to pretend to be talking on the phone in the hallway, to test how well the sound travels inside. Examine the floor for creaking sounds. If the floor creaks, it is likely that the parts are loose and will produce a creaking sound. Plan your visit during the noisiest time of the day. This will depend on the neighbourhood, and it may help to walk around the area before making an appointment to see the apartment, so that you have an idea of when the area becomes noisy. If there is a school nearby, it could be in the morning when the children are going to class or in the afternoon when the classes are over; if there is a busy highway — it may be during rush hour. Near a highway it may also be very noisy in the early hours of the morning, when the trucks and cars are driving past and the rest of the area is too quiet to drown the noise. Checking the area outside of the building at night may help with identifying potential sources of loud noise, such as bars. A noisy neighbourhood. Mississauga, Ontario, Canada.

Choose a quiet neighbourhood, away from schools and student housing, and select an apartment that faces away from the main street. Check the layout of the apartment carefully. When the surfaces shared with neighbours are minimal, the sound pollution is reduced. This is why corner top floor apartments are some of the most popular choices. If the living quarters are removed from the communal hallway, for example when the apartment has a long corridor, the noise from the outside is also reduced. Ask what material the building is made from. Concrete helps with reducing the noise. If, despite your careful checks you discover when you move in that the noise problem exists, you can reduce the amount of noise coming into your apartment by doing the following: Cover the floor and the walls with sound-absorbent materials, such as rugs, fabric wall-hangings, and tapestries. You can also install heavy curtains along the windows, extending to and covering the walls. It may improve the decor of the room as well. Noise is carried by solid objects through vibration, so minimizing it is key for reducing the sound that enters your apartment. Covering solid objects with fabrics such as tablecloths and choosing furniture with upholstery can help minimize vibrations of furniture. Heavy objects next to a wall may help reduce its vibration.

Bookshelves with books next to a wall can be used, for example. A household ceiling fan generates white noise White noise often helps drown the outside sounds, so using a device that produces this noise may help. It could be a white noise machine or a simple household fan. House fountains and aquariums with the water filters that are similar to a fountain can be useful as well. Noise travels well through the openings; to prevent that it is important to insulate the unit and to make sure that the doors, especially at the main entrance fit tightly to the floor or the carpet. You can check all the places where water and other pipes enter your apartment for potential openings. This will also help prevent insects from coming in and smells from other apartments to travel into yours. If the main source of noise is the street, insulating the windows may help, but if you do, you will only be able to get fresh air through the ventilation system, not from the outside. Some modern units have very good ventilation and the windows are sealed, so you will not have the choice in the matter, but your sound insulation will likely be good. Commercial soundproofing solutions are also an option, for example soundproofing foam and acoustic panels.

Speaking to the neighbours about the noise they make often helps as well, because many people do not realize how loud they are. Some property managers that rent out apartments require that the tenants cover their floors with carpeting, so it is possible to ask the management of the building to investigate whether the floor of the neighbours upstairs is, indeed, carpeted. Legislation Some countries try to regulate noise pollution through legislation; they often have fines associated with certain amounts of noise. In such cases residents can usually file a complaint about noise with the appropriate regulation body in their area, and this claim will be investigated. Some landlords also have rules prohibiting residents from making noise, such as playing musical instruments, during certain times. Restaurants and other establishments may have to apply for a license, which specifies how much noise is allowed and when. They may be only allowed to operate in certain areas of the city, and may also be required to soundproof their premises. Zoning, or restricting certain activities to a specified zone in the city during city planning, is also a way of limiting noise pollution. For example, the industrial zone with factories is often placed away from the houses, hospitals, and educational establishments.

Sound meter probe Measuring Sound Levels Sound levels are often measured to ensure that the levels are appropriate for the given purpose, for example that the microphones are loud enough for an event. The levels are also measured to ensure that the noise in the environment is safe for the people, who have to work in this environment. Sound Level Meters If the sound is above 85 dB for a prolonged period of time, hearing can become impaired. However, the threshold of pain for most people starts from 115 dB and can be as high as 140. People do not perceive sound that is too loud as dangerous, thus it is important to measure sound in environments that expose people to potentially loud sounds for a prolonged time. Often sound level meters are used in this case. Most of them are portable and affordable for the general public. Personal noise dosimeter Noise Dosimeters Dosimeters are used when the total amount of exposure to loud sounds needs to be measured. This could be useful for people who work in noisy environments and need to know whether they have to wear protective gear. Dosimeters are useful if the noise levels fluctuate throughout the day. They are generally worn by the workers, but not everyone accepts their use in the industry.

Some problems with using them include the ease to tamper with the device, potential interference with work, and dangers from the dosimeter’s cable getting caught in the machinery. Alternatively, sound level meters can be used instead to take measurements in different areas and at different times of the day, to create a sound map. This map allows one to estimate the daily sound level exposure for a given worker, based on his or her location. Newer dosimeters are designed to eliminate these problems by being small and unobtrusive, with no display, to discourage tampering with the data. Mitigating Noise It is paramount to reduce people’s exposure to the noise pollution in the factories, the airline industry, and in other high-noise environments, to prevent hearing loss. Noise can disrupt the concentration of the workers or make it impossible to hear warnings and alarms, resulting in accidents. Noise is also mediated for people’s comfort. If a sound level meter is not available, it is a good idea to use protection when one cannot be heard without shouting. Noise can be controlled by blocking it and by canceling the incoming noise with the generated outgoing noise. The former is passive while the latter is active noise cancellation.

Either method is chosen depending on the situation, but sometimes both can be combined. Several different types of passive noise cancellation protection can be combined as well. For example, ground crew at the airports may wear both ear plugs and ear muffs. Some places such as factories use sound baffles as well. They are made from absorbent material and prevent the sound from reflecting off surfaces and amplifying. Passive Noise Cancellation In passive noise cancelation materials that absorb noise are used. Most of the suggestions above for reducing noise in apartments work on this principle. In headphones such materials are foam and sponge. Noise-cancelling headphones Active Noise Cancellation This type of noise cancellation helps reduce up to about 20 dB of outside noise. The principle behind active noise cancelation is to cancel all or parts of the incoming sound wave by a sound wave that is of the same amplitude and is in an antiphase with the incoming wave. This emitted wave is created by the headphones. Airport worker wearing noise cancelling earmuffs. Toronto Pearson International Airport YYZ, Canada. This idea can be illustrated by imagining the swings.

When one person is pushing a moving swing from the back, and then another person comes and starts pushing it in the front with the equal amplitude and at the same time, their pushes will come in an antiphase and the movement of the swing will be cancelled, so it will stop. The noise cancellation equipment has to predict what the incoming sound would be, based on the sound that is prevalent in the environment, therefore this works well with the monotonous sound. If the noise changes constantly, then these headphones are less effective or do not work at all. The incoming sound is captured by the microphone, built into the headphones. Active noise cancellation technologies are also used in hearing protection aids for airport ground crew. Protective Gear Maintenance It is paramount to inspect personal protective gear such as earmuffs frequently, because wear in the foam and cracks in the plastic may allow unwanted sound. While the companies responsible for the workers have codes and regulations about maintaining the safety equipment, errors do occur so it is ultimately up to the worker to ensure personal safety. This article was written by Kateryna Yuri Unit Converter articles were edited and illustrated by Anatoly Zolotkov Learn Technical English with Our Videos!

You can use this online converter to convert between several hundred units (including metric, British and American) in 76 categories, or several thousand pairs including acceleration, area, electrical, energy, force, length, light, mass, mass flow, density, specific volume, power, pressure, stress, temperature, time, torque, velocity, viscosity, volume and capacity, volume flow, and more. Note: Integers (numbers without a decimal period or exponent notation) are considered accurate up to 15 digits and the maximum number of digits after the decimal point is 10. In this calculator, E notation is used to represent numbers that are too small or too large. E notation is an alternative format of the scientific notation a · 10x. For example: 1,103,000 = 1.103 · 106 = 1.103E+6. Here E (from exponent) represents “· 10^”, that is “times ten raised to the power of”. E-notation is commonly used in calculators and by scientists, mathematicians and engineers. Select the unit to convert from in the left box containing the list of units.

Select the unit to convert to in the right box containing the list of units. Enter the value (for example “15”) into the left From box. The result will appear in the Result box and in the To box. Alternatively, you can enter the value into the right To box and read the result of conversion in the From and Result boxes. If you have noticed an error in the text or calculations, or you need another converter, which you did not find here, please let us know ! Bel (acoustics) | Article about Bel (acoustics) by The Free Dictionary Bel (acoustics) | Article about Bel (acoustics) by The Free Dictionary decibel (dĕs`əbĕl', –bəl), abbr. dB, unit used to measure the loudness of sound sound, any disturbance that travels through an elastic medium such as air, ground, or water to be heard by the human ear. When a body vibrates, or moves back and forth (see vibration), the oscillation causes a periodic disturbance of the surrounding air or other medium that ..... Click the link for more information. . It is one tenth of a bel (named for A. G.

Bell), but the larger unit is rarely used. The decibel is a measure of sound intensity as a function of power ratio, with the difference in decibels between two sounds being given by dB=10 log10(P1/P2), where P1 and P2 are the power levels of the two sounds. The faintest audible sound, corresponding to a sound pressure of about 0.0002 dyne per sq cm, is arbitrarily assigned a value of 0 dB. The loudest sounds that can be tolerated by the human ear are about 120 dB. The level of normal conversation is about 50 to 60 dB. The decibel is also used to measure certain other quantities, such as power loss in telephone lines. Decibel A logarithmic unit used to express the magnitude of a change in level of power, voltage, current, or sound intensity. A decibel (dB) is 1/10 bel. In acoustics a step of 1 bel is too large for most uses. It is therefore the practice to express sound intensity in decibels. The level of a sound of intensity I in decibels relative to a reference intensity IR is given by notation (1).

(1) Because sound intensity is proportional to the square of sound pressure P, the level in decibels is given by Eq. (2). (2) The reference pressure is usually taken as 0.0002 dyne/cm2 or 0.0002 microbar. (The pressure of the Earth's atmosphere at sea level is approximately 1 bar.) See Sound pressure The neper is similar to the decibel but is based upon natural (napierian) logarithms. One neper is equal to 8.686 dB. Decibel a fractional unit of the bel (a unit of relative logarithmic value—the common logarithm of the ratio of two synonymous physical quantities, such as energy, power, or sound pressure). The decibel is equal to 0.1 bel. Symbols: Russian, db; international, dB. In practice the decibel is more often used than the bel, the basic unit.

decibel [′des·ə‚bel] (physics) A unit for describing the ratio of two powers or intensities, or the ratio of a power to a reference power; in the measurement of sound intensity, the pressure of the reference sound is usually taken as 2 × 10-4 dyne per square centimeter; equal to one-tenth bel; if P1 and P2 are two amounts of power, the first is said to be n decibels greater, where n = 10 log10(P1/ P2). Abbreviated dB. decibel The unit in which the level , 4 of various acoustical quantities is expressed. decibel 1. a unit for comparing two currents, voltages, or power levels, equal to one tenth of a bel 2. a similar unit for measuring the intensity of a sound. It is equal to ten times the logarithm to the base ten of the ratio of the intensity of the sound to be measured to the intensity of some reference sound, usually the lowest audible note of the same frequency deciBel A unit of measurement of the loudness or strength of a signal.

One deciBel is considered the smallest difference in sound level that the human ear can discern. Created in the early days of telephony as a way to measure cable and equipment performance and named after Alexander Graham Bell, deciBels (dBs) are a relative measurement derived from two signal levels: a reference input level and an observed output level. A deciBel is the logarithm of the ratio of the two levels. One Bel is when the output signal is 10x that of the input, and one deciBel is 1/10th of a Bel. A whisper is about 20 dB. A normal conversation is typically from 60 to 70 dB, and a noisy factory from 90 to 100 dB. Loud thunder is approximately 110 dB, and 120 dB borders on the threshold of pain. See dBm .

INCREASE IN POWER LEVELS (WATTS)Formula is dB=10*log(P1/P2)DeciBels Output Signal Strength 3dB 2x 6dB 4x 10dB (1 Bel) 10x 20dB 100x 30dB 1,000x 40db 10,000x ATTENUATION OF AMPLITUDE (VOLTS or AMPS)Formula is dB=20*log(A1/A2)DeciBels Output Signal Strength -3dB 0.707x -6dB 0.5x -10dB 0.316x -20dB 0.1x -30dB 0.032x -40db 0.010x Bels and Bells Quite a lot was named after Alexander Graham Bell. Throughout the 20th century, the Bell name was ubiquitous. It will live on with the deciBel.

decibel | unit of measurement | Britannica.com unit of measurement zhang Decibel, (dB), unit for expressing the ratio between two amounts of electric or acoustic power or for measuring the relative loudness of sounds. One decibel (0.1 bel) equals 10 times the common logarithm of the power ratio—i.e., doubling the intensity of a sound means an increase of a little more than three dB. In ordinary usage, specification of the intensity of a sound implies a comparison of the intensity of the sound with that of a sound just perceptible to the human ear. For example, a 90-dB, or 9-bel, sound is nine powers of 10 (i.e., 109, or 1,000,000,000) times more intense than a barely detectable sound. Decibels are also used to express the ratio of the magnitudes of two electric voltages or currents (or analogous acoustic quantities); in this usage one dB equals 20 times the common logarithm of the ratio. The term bel is derived from the name of Alexander Graham Bell , inventor of the telephone.

Learn More in these related articles: Alexander Graham Bell March 3, 1847 Edinburgh, Scotland August 2, 1922 Beinn Bhreagh, Cape Breton Island, Nova Scotia, Canada Scottish-born American inventor, scientist, and teacher of the deaf whose foremost accomplishments were the invention of the telephone (1876) and the refinement of the phonograph (1886). Audiometry ...intensity for each frequency at which the person reports being just able to hear the tone 50 percent of the time. For example, one who hears the tone of 4,000 hertz only half the time at the 40-decibel setting has a 40-decibel hearing level for that frequency—i.e., a threshold 40 decibels above the normal threshold. A graph showing the hearing level for each ear by octaves and half... The physiology of hearing ...tympanic membrane. The greater their amplitude or strength, the greater is the pressure or intensity, and consequently the loudness, of the sound. The intensity of sound is measured and reported in decibels (dB), a unit that expresses the relative magnitude of a sound on a logarithmic scale.

Stated in another way, the decibel is a unit for comparing the intensity of any given sound with a... 8 References found in Britannica Articles Assorted References Decibel - Student Encyclopedia (Ages 11 and up) one tenth of a bel; unit of measure of loudness of sounds to normal human ears; because the power of the ear to distinguish differences in loudness decreases as volume increases, the bel scale is made logarithmic; each unit is 10 times the preceding one; thus a barely audible whisper measures one bel (10 decibels) and a speeding express train about 10 bels (100 decibels), though the train generates 10 billion times as much sound energy; in practice, measurements are made with a special sound meter (acoustimeter) containing numerous electrical circuits whose aggregate sensitivity to pitch and loudness corresponds to that of the human ear Article History Corrections? Updates? Help us improve this article! Contact our editors with your feedback. MEDIA FOR: You have successfully emailed this. Error when sending the email. Try again later. Edit Mode Submit Tips For Editing We welcome suggested improvements to any of our articles.

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Close Date Published: July 20, 1998 URL: Access Date: January 20, 2017 Share True or False True or False This activity contains 10 questions. Sound is any change in pressure that can be detected by the ear. The unit of measurement for sound is the decibel (one-tenth of a bel). False The threshold of hearing is the maximum level of sound that can be perceived without experiencing pain. The fundamental hazard associated with excessive noise is hearing loss. False To decrease the risk of hearing loss, exposure to noise should be limited to a maximum eight-hour time-weighted average of 90 dBA. Bel (Acustics) | definition of Bel (Acustics) by Medical dictionary Bel (Acustics) | definition of Bel (Acustics) by Medical dictionary decibel [des´ĭ-bel] a unit of relative power intensity equal to one tenth of a bel, used for electric or acoustic power measurements; one decibel equals approximately the smallest difference in acoustic power the human ear can detect and an increase of 10 decibels approximately doubles the loudness of a sound. Abbreviated dB or db. Examples of decibel levels in everyday situations.

From Frazier et al., 1996. dec·i·bel (dB, db), (des'i-bel), Avoid the mispronunciation des'i-b'l. One tenth of a bel; unit for expressing the relative intensity of sound on a logarithmic scale. [L. decimus, tenth, + bel] decibel /dec·i·bel/ (des´ĭ-bel) a unit used to express the ratio of two powers, usually electric or acoustic powers, equal to one-tenth of a bel; one decibel equals approximately the smallest difference in acoustic power the human ear can detect. decibel (dB) [des′əbəl] Etymology: L, decimus, one tenth, bel, Alexander G. Bell, Canadian inventor, 1847-1922 a unit of measure of the intensity of sound. A decibel is one tenth of 1 bel (B); an increase of 1 B is perceived as a 10-fold increase in loudness, based on a sound-pressure reference level of 0.0002 dyne/cm2, or 20 micropascals.

dec·i·bel (dB) (des'i-bĕl) One tenth of a bel; unit for expressing the relative loudness of sound on a logarithmic scale. [L. decimus, tenth, + bel] decibel A logarithmic unit of comparison between a standard power level and an observed level. The decibel is not a unit of sound intensity but is widely used to compare a noise level with a very low standard reference level near the limit of audibility, and to compare electrical power levels. A tenth of a bel. Decibel A unit of measure for expressing the loudness of a sound. Normal speech is typically spoken in the range of about 20-50 decibels. Decibel | definition of decibel by Medical dictionary Decibel | definition of decibel by Medical dictionary decibel [des´ĭ-bel] a unit of relative power intensity equal to one tenth of a bel, used for electric or acoustic power measurements; one decibel equals approximately the smallest difference in acoustic power the human ear can detect and an increase of 10 decibels approximately doubles the loudness of a sound. Abbreviated dB or db. Examples of decibel levels in everyday situations.

From Frazier et al., 1996. dec·i·bel (dB, db), (des'i-bel), Avoid the mispronunciation des'i-b'l. One tenth of a bel; unit for expressing the relative intensity of sound on a logarithmic scale. [L. decimus, tenth, + bel] decibel /dec·i·bel/ (des´ĭ-bel) a unit used to express the ratio of two powers, usually electric or acoustic powers, equal to one-tenth of a bel; one decibel equals approximately the smallest difference in acoustic power the human ear can detect. decibel (dB) [des′əbəl] Etymology: L, decimus, one tenth, bel, Alexander G. Bell, Canadian inventor, 1847-1922 a unit of measure of the intensity of sound. A decibel is one tenth of 1 bel (B); an increase of 1 B is perceived as a 10-fold increase in loudness, based on a sound-pressure reference level of 0.0002 dyne/cm2, or 20 micropascals.

dec·i·bel (dB) (des'i-bĕl) One tenth of a bel; unit for expressing the relative loudness of sound on a logarithmic scale. [L. decimus, tenth, + bel] decibel A logarithmic unit of comparison between a standard power level and an observed level. The decibel is not a unit of sound intensity but is widely used to compare a noise level with a very low standard reference level near the limit of audibility, and to compare electrical power levels. A tenth of a bel. Decibel A unit of measure for expressing the loudness of a sound. Normal speech is typically spoken in the range of about 20-50 decibels. Decibel - definition of decibel by The Free Dictionary Decibel - definition of decibel by The Free Dictionary range of human hearing in decibels de·ci·bel (dĕs′ə-bəl, -bĕl′) n. Abbr. dB A unit used to express relative difference in power or intensity, usually between two acoustic or electric signals, equal to ten times the common logarithm of the ratio of the two levels. (ˈdɛsɪˌbɛl) n 1.

(Units) a unit for comparing two currents, voltages, or power levels, equal to one tenth of a bel 2. (Units) a similar unit for measuring the intensity of a sound. It is equal to ten times the logarithm to the base ten of the ratio of the intensity of the sound to be measured to the intensity of some reference sound, usually the lowest audible note of the same frequency Abbreviation: dB (ˈdɛs əˌbɛl, -bəl) n. a unit used to express differences in power, esp. in acoustics or electronics: equal to ten times the common logarithm of the ratio of two signals. Abbr.: dB de·ci·bel (dĕs′ə-bəl) A unit used to measure the loudness or intensity of a sound. The speaking voice of most people ranges from 45 to 75 decibels. See Note at sound 1. decibel 1. A logarithmic unit of sound intensity. 2. (dB) A measure of relative sound intensity. ThesaurusAntonymsRelated WordsSynonymsLegend:

Question: Which unit of sound is one tenth of a bel
Answer: Decibel